Origin of Radiation and Effects of Enclosure Ventilation on Combustion and the Composition of Smoke - Assignment Example

1- Radiation is the result of fire combustion process. Main features of radiation include the transfer of heat in the surroundings in the form of fireball. Radiation as a process has got a certain field. The radiation fields have their own flux and impact. A fraction of heat energy is converted into the radiation process. Radiation gases produced in the combustion process are the nitrogen dioxide, sulfur dioxide and carbon dioxide with certain elements of carbon monoxide. The volume of emitted radiation gases depends upon the volume of combustion process. The width of the gases radiation depends upon the volume of combustion (Goreniya i Vzryva 1999 pp12-23). The radiation of heat from one building to the other building requires a medium. The medium can be any substance and the nature of substance of the adjoining buildings determines the impact and deterioration due to the heat transfer. It is, therefore, necessary that the buildings should be sufficiently separated from each other in order to offset the impact of radiation from one building to the other building. As discussed, the spaces between the buildings provide for the empty and void space which is only filled with the air molecules. These air molecules touching with the burning building take away the heat energy from them and take it away through the process of diffusion in the air. Therefore, the space between two buildings is the empty medium that prevents the transfer of heat from one building to the other building (ASTM 2007, pp 14). Since the volume, flux and field of radiation process is dependent upon the fire combustion and the space requirement of the buildings should be determined by the fire engineers according to the fire resistance of the materials used in the buildings. 2- Effects of enclosure ventilation on combustion and the composition of smoke are given as follows. Enclosure ventilation means a purposeful and mechanical arrangement to allow the fresh air containing oxygen to go into the enclosed buildings and to replace the already contained gases in the building with fresh ones. These ventilation arrangements can be the ventilators, windows, balconies, smoke suction devices or any other open spaces for exchange of gases in the internal and external environment of a building (ASTM 2004, pp 24). During the combustion various toxic gases emit from the flames, smoke and the burning material depending upon the nature of substance that is under combustion. Usually in the common buildings when they are under fire, the furniture, fixtures, carpets, electric installations, curtains, beds, clothes and plastic materials catch the fire and an unending combustion process starts. Enclosure ventilation can have both types of impacts on the combustion process within a building. The combustion creates toxic gases and consumes oxygen for converting it into the heat energy and making different chemicals during the endothermic and exothermic process of chemical reactions at the same time. The enclosure ventilation, either, readily supplies fresh oxygen and the combustion is flared up or the combustion changes its chemical course due to the diffusion of toxic gases like nitrogen dioxide, sulfur dioxide, carbon dioxide and carbon mono oxide etc, to escape through the enclosure ventilation into the air. The impact of enclosure ventilation on the quality of smoke is positive during the combustion. Because it is diluted and the particles of soot are more separated from each other due to the mixture of fresh air from the enclosure ventilators. Thus the concentration of flaming region of fire becomes limited due to enclosure ventilators (ASTM 2002, pp 15). In this way the combustion becomes less hazardous. However, it is most important to note that enclosure ventilations depend for their impacts upon the concentration of combustion, nature, quality and quantity of the combustible materials within a building. Anyway enclosure ventilation is a necessary arrangement to alter the impact of combustion within a building in case of a fire emergency. 3- The production of smoke is effected by varying compartment/building geometry and fire location. Performance based designs of the buildings and their geometry has a definite impact on the production of smoke. This is because smoke is the function of combustion, the materials being burnt, and the availability of oxygen within a geometric design of the building that would in burning the materials. The smoke is the air and soot with the addition of certain other gases. Therefore, the varying compartments and the buildings maps and geometries have a direct impact on the production of smoke and the corresponding production of plumes of the smoke (Childs, K.W. 1997, pp 35). Basically air is shapeless and diffusible. Therefore, the structure of plume in a building depends upon the heat energy of the particle floating in a building apartment according to its geometrical design. The particles of smoke in a plume remain in a field of attraction because of positive and negative charges attracting each other. The axis-symmetric plumes, adhered plumes, spill plumes can be compared with each other on the basis of their shapes and mass flow of gases within the plumes (Factory Mutual Research Corporation 1998, pp 43). The spill plumes change into the axis-symmetrical plumes after travelling for a certain distance in a linear upward direction of the buildings. The smoke having no building geometry to shape its plume will be called adhering plume as it will adhere to the walls. Plumes generated from large openings get the shape of adhering plumes. 4- There are the four functions of smoke control. Smoke control in the buildings is done to reduce the danger of suffocation and toxicity for the occupants of the affected building. Smoke control is also done for containing the dangers of its impact on the entire building and the adjacent buildings. Smoke control is also done for the protection of air outside the buildings from pollution. There are many methods to achieve an effective smoke control even in the chimneys of the factories where incinerators are used for combustion of waste materials. The dust particles and ignition products of the smoke are controlled from diffusion in the air through insertion of electrostatic gunny bags. The particles of the smoke get positively charged due to the heat while, the gunny bags are artificially negatively charged (G. M. Makhviladze, J. P. Roberts and S. E. Yakush, 1996, pp 24). The smoke particles stick to these bags in the chimneys and filter down in the form of ash. Smoke control is required in the event of fire incidences, the factories where the combustible materials are ignited and in the incineration plants. However, smoke control modeling is done with the following manners. The other method of smoke control in the buildings is enclosure ventilations. This is an inbuilt solution of smoke control through which the plumes of smoke are given way to vent out through windows, ventilators, exhaust fans, balconies and open spaces. Smoke detectors are also employed in the sensitive places so that the electric smoke control alarms automatically start ringing up and the modern smoke control mechanisms are switched on to save the buildings and their inmates from the dangers of smoke. 1-Analysis of the movement of the particles in the smoke 2-Design for the Smoke control system 3-Test of the smoke movement 4-Commissioning of the smoke control system Therefore, in the fire and hazard engineering smoke control has not only become an essential subject but also a technique which has central place in the fire and rescue management. 5- Temperature to heat ratio of different materials is called the standard fire curve. The standards of these curves are different for various materials including metals, glass, aluminum, iron, plastics, sands, steel, concrete and inert materials. The building materials used are pretested for their heat resistibility by the way of measuring their temperature when put across intense heats produced by the fire (Jones, W.W., Peacock, R.D., Forney, G. P., and Reneke, 2005, pp 39). This is because the composition, texture, structure and strength of building materials in various geographic locations are different. Besides, this factor the climates, weather an temperatures in different seasons of the year along with moisture content are different in different countries. This is because of this reason that the standard curves for heat resistance for different building materials if different for different regions of the world. The above approach of the standard curve varies for the onshore and offshore countries because of the simple reason that the building materials have different strength, texture and consistency due to climatic and geographic conditions apart from each other in onshore and offshore countries of the world. Actually the fire resistance rating truly means the time duration in which the fire protection system can resist the fire resistance tests. This is simply a measurement of time taken by the passive fire resistance system can oppose and withstand the proper standard fires resistance tests. Normally in all countries of the world, while constructing the buildings, building elements curve. For the constructing the exterior systems the hydrocarbon curve is used. These hydrocarbon curve materials are almost same in every region of the world (NFPA 2006, pp 12). The major difference between the different countries of the world is that the use of pipes, these pipes guard and shields the furnaces from the inside. While the other types of pipes known as the ISO based European curves are a little bit hotter and the results were different from the pipes when these ISO based European tests were tested. While, testing the pipes, to be used in the buildings, the hose-stream is also added in order to add strength and firmness to the pipes. As there are different methods of testing the materials and systems, all over the world, the organizations and associations which market such systems and product, also have to take many different tests in different regions of the world. References: 1. ASTM E 119, 2007, pp 14, Standard Test Methods for Fire Tests of Building Construction Materials, ASTM International, West Conshohocken. 2. ASTM E 84, 2002, pp15, Standard Test Methods for Fire Tests of Building Construction Materials, ASTM International, West Conshohocken. 3. Childs, K.W. 1998, pp 35, HEATING 7: Multidimensional, Finite-Difference Heat Conduction Analysis Code System, Technical Report PSR-199, Oak Ridge National Laboratory. 4. Factory Mutual Research Corporation, 1998, pp 43, 1151 Boston-Providence Turnpike, Norwood, MA 02062, USA. 5. Goreniya i Vzryva, Vol. 35, July–August 1999, pp. 12–23. Multidimensional, Finite-Difference Heat Conduction Analysis Code System, Technical Report PSR-199, Oak Ridge National Laboratory. 6. G. M. Makhviladze, J. P. Roberts and S. E. Yakush, 1996, pp 24. Multidimensional, Finite-Difference Heat Conduction Analysis Code System, Technical Report PSR-199, Oak Ridge National Laboratory. 8. Institute of Mechanical Problems, Russian Academy of Sciences, 117526 Moscow 9.Jones, W.W., Peacock, R.D., Forney, G. P., and Reneke, 2005, pp 39, CFAST - Consolidated Model of Fire Growth and Smoke Transport (Version 6) User’s Guide, NIST Special Publication. 10.NFPA 286, 2006, pp 12, Standard Methods of Fire Tests for Evaluating Contribution of Wall and Ceiling Interior Finish to Room Fire Growth, National Fire Protection Association. 9- Read More